I have never felt after drinking tea that I can have the power of being able to work late at night. Neither have I felt that it helps me to be awake while working or keeping eyes opened while I am not in mood for sleeping.

Drinking tea, then, does not helps me to stay awake.

Is it the nature of the tea itself, or does it have to do with how the body processes caffeine?

3 Answers
3

It could be tolerance if other caffeinated beverages are usually consumed, however it also depends on the type of tea itself, and other properties, such as how long the tea has steeped for.

For example, brewed black tea can have anywhere from 14-61 mg of caffeine, which is a large range and depends on which tea you are drinking specifically. Whereas if you were drinking green tea that has not been steeped for long, it can have 24-40 mg of caffeine, which at the lower range will probably not help you stay awake.

The actual caffeine content of the same coffee drink can vary from day to day — even at the same coffee shop — because of various factors, such as roasting and grinding, as well as brewing time. The caffeine content of tea also is affected by how long it's brewed.

Another idea I have come across is that caffeine absorption is much slower with tea, though my source is a Good Eats Episode. The relevant information can be found at approximately 19 min. Maybe it's true, maybe it's not, but regardless, it's a great episode to watch if you are into tea.

What is happening to you is 'tolerance'. It is a term used in pharmacology. It is a phenomenon by which a drug/medicine becomes less effective the body gets used to it. One explanation is less receptors for that drug are manufactured because of negative feedback. You may have developed tolerance to tea.